Abstract： Objective To investigate the effect of oxyhemoglobin (OxyHb) on the cell density and DNA - binding activity of nuclear factor (NF) - κB in the cultured vascular smooth muscle cells(VSMCs). Methods The cultured VSMCs were treated with different concentration from 1 to 100 μmol/L of OxyHb. The cell density was measured. DNA - binding activity of NF -κB was detected using electrophoretic mobility shift assay (EMSA). Results Morphological alterations occurred in the VSMCs after treatment with OxyHb. The concentration of OxyHb at 100 μmol/L produced a significant decrease in cell density at 24 hour, and 10 μmol/L at 72 hour. DNA - binding activity of NF -κB was increased after treatment with OxyHb, and peaked at 10 and 50 μmol/L Conclusion Alteration of NF -κB DNA - binding activity occurred in the VSMCs treating with OxyHb, which suggests that NF -κB pathway in the cerebrovascular smooth muscle cells may be involved in the pathogenesis of cerebral vasospasm.